Trial OSCE exam: 'Sarah&Clarence3' by ClaireGo

You are taking part in a trial exam created by ClaireGo. There are 8 OSCEs in this exam (80 minutes).

You have 3 minutes reading time. This OSCE will run for a maximum of 7 minutes.


A junior registrar comes to you for some advice on ECG interpretation. They assisted in a case of a 52-year-old man who presented with palpitations and mild dizziness and was treated a few days prior. They found the ECG difficult to interpret.

View attached:   Attachment 1

Instructions for the candidate

You are the consultant allocated to clinical teaching and you are meeting the registrar in non-clinical time. You are to interpret the ECG, answer any relevant questions and provide pearls for differentiating future similar ECGs.

Domains being examined

  • Medical Expertise
  • Communication
  • Scholarship and Teaching
The candidate has 3 minutes reading time. This OSCE is expected to run for a maximum of 7 minutes.

For the actor

You are a junior registrar and are fairly competent in general and with ECGs.

This patient was thought to have VT and was treated successfully with DC cardioversion, then admitted under cardiology.

You wanted to know how to tell this was VT and not another broad complex tachyarrythmia, such as SVT with aberrancy.

You want to know how differentiating SVT with aberrancy from VT would affect management.

For the examiner


Domains Assessment Objectives

Medical Expertise
ECG interpretation, specifically differentiation of VT and SVT with aberrancy
Management of broad complex tachycardia

Clear and articulate communication

Scholarship and Teaching
Appropriate teaching style and level

Other Assessment Notes

This ECG and the detail below comes from:

Patient features more likely VT:
-Age > 35 (positive predictive value of 85%)
-Structural heart disease
-Ischaemic heart disease
-Previous MI
-Congestive heart failure
-Family history of sudden cardiac death (suggesting conditions such as HOCM, congenital long QT syndrome, Brugada syndrome or arrhythmogenic right ventricular dysplasia that are associated with episodes of VT)

ECG features more likely VT:
-Extreme axis deviation (“northwest axis”)
-Absence of typical RBBB or LBBB morphology
-Positive or negative concordance throughout the chest leads, i.e. leads V1-6 show entirely positive (R) or entirely negative (QS) complexes, with no RS complexes seen.
-AV dissociation (P and QRS complexes at different rates)
-Very broad complexes (>160ms)
---Brugada’s sign – The distance from the onset of the QRS complex to the nadir of the S-wave is > 100ms
-Capture beats — occur when the sinoatrial node transiently ‘captures’ the ventricles, in the midst of AV dissociation, to produce a QRS complex of normal duration.
-Fusion beats — occur when a sinus and ventricular beat coincides to produce a hybrid complex.
-QRS morphology changes:
---Josephson’s sign – Notching near the nadir of the S-wave
---RSR’ complexes with a taller left rabbit ear. This is the most specific finding in favour of VT. This is in contrast to RBBB, where the right rabbit ear is taller.

ECG changes suggestive of SVT (with aberrancy)
-Previous ECGs show a bundle branch block pattern with identical morphology to the broad complex tachycardia.
-Previous ECGs show evidence of WPW (short PR < 120ms, broad QRS, delta wave).
-The patient has a history of paroxysmal tachycardias that have been successfully terminated with adenosine or vagal manoeuvres

At the end of the day (or quite soon after they present), treat as VT.